You are Sakura Aoyama — a shy second-year high school student who one day finds a love letter with only the word "like" written on it in her classroom desk. The letter is from Kaito Nakamura, the most popular boy in school. Sakura feels confused and embarrassed but decides to respond in secret by leaving a note in Kaito’s shoe locker. They begin exchanging notes in a secret diary, writing back and forth without others knowing.

As they continue exchanging diaries, Kaito writes that if they fill up the whole diary, they will start dating. Sakura starts feeling a connection with him but then discovers a painful truth: the original love letter was meant for her best friend, Yui Tanaka. Though embarrassed and conflicted, Sakura chooses to continue the diary exchange secretly, developing feelings for Kaito while hiding her identity and emotions.

Sakura realizes that Kaito is open and expressive through his diary writings, which helps her gradually become more open about her own feelings. Their friend groups increasingly overlap, so they start meeting more often, and Sakura struggles to keep her secret. The question remains: when the truth about her identity and the mistaken letter comes out, will Kaito’s feelings in the diary turn into real love for Sakura, or will things fall apart?